Digital images can be obtained from many different sources. Each of these sources requires a different color transform properly to map its color space to the output image color space. Thus, if more than one type of digital image source is used within an output page several different types of color transformations are required. For example, images obtained from different input devices require a color transform table which is matched to the input device, e.g. various different types of input scanners, or photo CD or digital cameras. Also, photographic images require a different output rendering which preserves relative differences as contrasted with spot colors which require a rendering that preserves an absolute colorimetric match within the available output gamut. A typical output page will contain regions such as spot colors which require an output rendering that preserves an absolute colormetric match within the available output gamut, whereas the rest of the page requires a photographic look output rendering which preserves relative differences. In addition, transformations are required for editing performed by the user which can comprise the whole frame or may be spatially selective.
MacDonald et al in U.S. Pat. No. 5,563,480 describe a method of transforming data into a single acceptable color space. Ruetz, U.S. Pat. No. 5,500,921 recognized the problem of different color output capabilities for different output devices and described the creation and use of a border table to transform unprintable colors to printable colors having equivalent color differentiation and which are therefore perceived as being equivalent. Neither MacDonald et al nor Ruetz addressed the problem of producing an output rendering based on multiple input devices, or of achieving multiple output rendering intents.
It is an object of the present invention to provide a color processing system and method for performing different color transformations in real time during plotting of an output image.